My mom has the 8.9" Aspire One w/ 6-cell and XP. Runs fine and she likes it, though the touchpad is way too small and the buttons are stiff, so I got her a Revolution VX Nano mouse (has a tiny receiver so it doesn't stick out). Keyboard is one of those fail bi-lingual things which is utterly annoying and it's also a bit too small.

Depending on your budget, maybe look at the newer 10/11" models since then you should get a better sized keyboard and also a 9" screen can be hard at times since rather tiny.

I guess what you should do is find the models in store and let your GF try them out to make sure she can adapt to the keyboard/touchpad.